Pneumatic separation table



Oct. 8, 1929.

6. RAW

PNEUMATIC SEPARATION TABLE Filed May 1928 Patented Oct. 8, 1929 UNITED STATES GEORGE RAW, OF NEW WASHINGTON, ENGLAND PNEUMATIC SEPARATION TABLE 7 Application filed May 14, 1928, Serial No. 277,771, and in Great Britain May 26, 1927.

This invention relates to apparatus for use where the dry separation of solid divided materials is preferable as in the dry separation of ores from their gangue and the dry cleaning of coal, and the invention is concerned with apparatus of the kind comprising a pervious trough-like table or deck on which a bed of the materials is subjected to the action of air or other gaseous fluid so as to 10 cause material of relatively low specific gravity to stratify above material of higher specific gravity.

In cases where separation of the less dense from the denser material, after stratification,

is effected by lateral discharge over the sides of the table and the latter is restricted forwardly so as to maintain a suitable thickness of the bed, it has been observed that there is a slight tendency, particularly with gradually converging tables, for the denser material to accumulate at the sides and thus cause squeezing or discharge of this material also over the sides.

One object of this invention therefore is to overcome this tendency for the denser material to be squeezed over the sides of the table and to ensure that only material of relatively low specific gravity is discharged at the sides as desired.

A further object is to produce more favourable flow of the material along the table or deck and another object is to enable the materials to be subjected to a series of independent stratifying actions in succeeding parts of the table as the materials of different densities move forward together.

An additional and, moreover, important object is to provide a form of separating table which is particularly suited for the carrying out of the process of separation described in the specification accompanying my prior patent application, Serial No. 186,474, filed 25th April, 1927. I I

More specifically, the invention provides a separating table or deck which is restricted forwardly by one or more relatively sharp contractions of its width to maintain desired thickness of the bed, and in theneighbourhood of the contraction or contractions of 59 width is provided with an imperforate and downwardly inclined portion on its bottom for giving relief to the denser material at the point or points where building up of the bed takes place. The arrangement thus described not only avoids relatively long convergences of the table which are liable to produce the squeezing effect aforesaid, but in addition it will be seen that as the material reaches and moves over the imperforate parts it becomes quiescent for ust a short period of time while partaking of a slight downward and forward movement, and this is found to give just that amount of relief to the denser material, as will prevent accumulation thereof in any part of the table. Y

For the purpose of enabling the invention and its objects to be more readily understood reference will now be made to the following detailed description taken in conjunction with the accompanying drawing wherein 7 Figure 1 is a general View including a separating table in accordance with these improvements and showing suspension, vibrating and feed mechanism for the table and coal and stone discharge chutes, t

Figure 2 is a central longitudinal section of the table on a larger scale than Figure 1, the section being along the line 2-2 of Figure 8.

Figure 3 is a plan of the table,and

Figure 4 is a transverse section on the line 44t of Figure 2. c

The separating table shown in the drawings comprises several parallel-sided portions a, a, a, of different widths decreasing for- 5 wardly of the table, and the sides 6 at the junction of these parts, comprise inwardly inclined parts 0 which provide relatively sharp contractions of the width of the table as compared with contraction by long and gradual convergence, Each portion a has a perforate bottom (Z which is only diagrammatically shown but suitably consists of perforated metal plate, and in the neighbourhood of the inwardly inclined parts 0 ofthe sides, these bottom portions d are joined by imperforate members 6 having inclined upper surfaces which constitute shallow downward and forward inclinations in the bottom of the table.

If desired, the foremost parallel sided portion a of the table may be hinged to the remainder of the table and constitute a stone cell of the nature referred to in my previous specification. A discharge chute f for the stone or denser material is pivotally mounted at g at the forward end of this portion of the table.

The table comprises a frame it on which parts aforesaid are mounted and it is suspended by Outriggers j on this frame from spring-steel hangers is which allow it to be vibrated by the eccentric and coni'iecting-rod mechanism Z (see Figure 1). The suspension mechanism is suitably adapted to allow of variation of the inclination of the table but asthis and the vibrating mechanism may be of any known construction, such as that described in my prior specification aforesaid, it is thought that further description thereof is unnecessary. The inclination of the discharge chute f may be varied by the screw and nut mechanism at m. As in my previous specification, the table would be arranged over asuitable air box (not shown) and the lower edge of the frame it would have connection with the upper edge of this air box by the usual flexible part a (Figure 1) so as to allow vibration of the table with respect to the air box which is generally stationary.

Immediately before each contraction and downward slope of the table, it is preferred to place a V-form skimmer 0 to effect discharge of material of lesser density through the sidesof the table and a similar skimmer is also placed just before the extreme forward end of the table. Generally, it is only necessary-to have the shimmers in the positions indicatedbut an extra skimmer p may be placed over the foremost part aof the table. The skimmers discharge through gaps win the upstanding sides 6 of the table and, as in my prior specification aforesaid, they may each have a rearwardly extending and perforate foot portion 8 to assist the mechanical separation and discharge of the upper layer of material on respective parts of the table. The skimmers and their feet portions 3 may be supported at the point of the a by bolts or other members i" slung from supports a extending across the table at suitable points, and the portions 6 of the table bottom may, in plan, follow the V contour of the skimmers 0 so as to direct the denser material more favourably into the next succeeding portion a of the table. 7

At its rearend, the table may be fitted with ashield device o extending along the upstanding rear end wall to and for a short distance along the sides, and this will direct the feed of material on to the table. any suitabie form of feed mechanism may be used, and a roller feed device is more or less diagrammatically indicated at m in Figure 1. Discharge lips or plates 3 may extend from the sides of the table to direct the material, discharged at the sides of the table, into suitable delivery chutes shown partly at a and the denser material may pass from the discharge chute 7 into a delivery chute Z, the material being directed by these delivery chutes into trucks or to other places of delivery. The portion of the bottom of the table which, in plan, is within the V of the foremost skimmer 0, immediately before the discharge chute f, maybe imperforate to provide a dead area to mark off the area where it is desired to merge from the fluid material on the table to the dead material in the stone chute. This imperforate part would not alter the pressure of the air in any part of the bed where the material is required to be fluid In operation, the materials to be separated are fed-on to the rear end of the table by the feed devicew in suitably regulated manner to form abed of suitable thickness on the table. Meanwhile the latter is subjected to vibratory iotion by the eccentric and connecting rod mechanism Z and air under pressure of pulsating or uniform nature is supplied to the air box beneath the table. This may be effected by any suitable means, for example, the arrangements described in my prior specification aforesaid. The materialson the table become attenuated under the action of the air and they stratify according to their specific gravities, the least dense material uppermost and that of greater specific gravity below. it the forward end ofeach portion (4- of the table the skimmers 0 function to discharge the upper layer of material tnrough the gaps r in the sides of the table. The extra skimmer p at about the centre of the foremost part a of the table assists the discharge of so-called middlings. it also slightly thins out the bed of middlings and stone to more appropriate depth having regard to available air pressure and the greater density of the materials forming this bed. Upsta-nding plates 2 may be provided on the discharge lips or plates y in the region of the foremost part of the table, see Figure 3, :to confine the delivery of the middlings to the foremost of the delivery chutes a. The stone or densest material passes from the forward end of the table by the discharge chute f and thence into the delivery chute 1. Any desired inclination may be given to the discharge chute f by the screw and nut mechanism 112- so as to obtain appropriate control of the speed of movement, generally, of the denser material along the table.

It may be observed that stratification action takes place on each of the portions or zones a of the table. i-is the members 6 are iinpei forate and provide a quiescent region, it may be said that each portion or Zone a of the table with its skimmer or Skimmers is a separate entity, so that the table in reality is a combination of three different separating decks or tables operating in series under the influence .of the same pneumatic pressure. In any case, the imperforate inclinations at e relieve undesirable squeezing effect aforesaid, for it will be understood that when the denser material reaches these parts, it is temporarily freed from the action of the air pressure and part-akes of a small downward movement which together gives slight relief to the denser material in the portion or zone of the table to the rear, this relieving movement constantly taking place all the time the table is operating. The fact that'the upper surface of the members 6 is of low height or inclination prevents upsetting the degree of stratification already achieved and these members do not affect the desired statical conditions in the bed when working in accord ance with my prior process aforesaid. The inclined parts 00f the sides of the table cause the thickness of the bed to be maintained after passing from beneath each of the first two skimmers 0 to the next portion of the table and as the sides of the table are of preferably uniform height along the length of the table a substantially even thickness of bed can thus be maintained over the whole pervious area of the table as required in my prior process aforesaid.

In the above description of one favourable construction of table according to this inven tion I have indicated suitable mechanism for imparting vibratory movement to the table in operation, but obviously other forms of mechanism may be used for this purpose. Or as a modification the table may be stationarlly mounted, in which case pulsating pressure of the air or other gaseous fluid, in con unction with an appropriately increased inclination of the table, would be used to cause the desired forward flow of the materials over the table. I wish it to be understood that I do not limit myself to the particular form of table described as various modifications may be made without departing from the scope of the invention set forth in the appended claims.

I claim 1. A table for the pneumatic separation of solid materials of different specific gravities, comprising in combination a deck surface composed of a plurality of pervious parts of difierent widths arranged at different levels, an imperforate and downwardly inclined slope part joining adjacent pervious parts, upstanding sides for said deck surface relatively sharply contracted towards each other in the neighbourhood of the slope part, and means for discharging material laterally from the table.

2. A table for the pneumatic separation of solid materials of different specific gravities, comprising in combination a deck surface composed of a plurality of substantially parallel-edged pervious parts of different widths at a relatively-sharp angle in the neighbourhood of the slope part, and means for discharging material laterally from the table.

3. A table for the pneumatic separation of solid materials of different specific gravities comprising in combination a deck surface composed of a series of substantially paralleledged pervious parts of different widths arranged at different levels, imperforate and downwardly inclined slope parts joining adjacent pervious parts, upstanding sides for said deck surface inclined towards each other at arelatively sharp angle in the neighbourhood of the slope parts, and means for discharging material laterally from the table immediately before each slope part.

4. A table for the pneumatic separation of solidmaterials of different specific gravities, comprising in combination a deck surface composed of a plurality of pervious parts of different widths arranged at different levels, an imperforate and downwardly inclined slope part joining adjacent pervious parts, upstanding sides for said deck surface relatively sharply inclined towards each other in the neighbhourhood of the slope part, and skimmers with rearwardly extending and perforate foot members situated at the forward end of the pervious deck parts for discharging material laterally from the table.

5. A table for the pneumatic separation of solid materials of different specific gravities, comprising in combination a plurality of pervious deck parts of different widths arranged at different levels, a V-form skimmer disposed over the forward end of the pervious parts, an imperforate and downwardly inclined slope part joining adjacent pervious parts and following the contour of the adjacent skimmer in plan, and upstanding table sides relatively sharply contracted towards each otherin the neighborhood of said slope art.

6. A table for the pneumatic separation of solid materials of different specific gravities, comprising in combination a plurality of pervious deck parts of different widths arranged at different levels, a V-form skimmer disposed over the forward end of the pervious parts, an imperforate and downwardly inclined slope part joining adjacent pervious parts and following thevcontour of the adjacent skimmer in plan, an imperforate deck part at the forward end of the table beyond the foremost skimmer, and upstanding table sides relatively sharply contracted towards each other in the neighbourhood of said slope part. I I

7. A table for the pneumatic separation of solid materials of different specific gravities, comprising in combination a deck surface composed of a series of substantially paralleledged pervious parts of difierent Widths arranged at different levels, imperforate and downwardly inclined slope parts joining adjacent pervious parts upstanding sides for said deck surface contracted towards each other in the neighbourhood of said slope parts, a skimmer disposed just before each slope part for discharging material laterally from'the table, and an additional skimmer disposed over the foremost pervious part of the table.

8. A table for the pneumatic separation of solid materials of different specific gravities, comprising'in combination a deck surface composed of a series of substantially p aralleledged pcrvious parts of different Widths arranged at different levels, imperforate and downwardly inclined slope par s joining adjacent pervious parts, upstanding deck sides of substantially uniform height and inclined towards each other at a relatively sharp angle inthe neighborhood of said slope parts, and Skimmers disposed just before each of said slope parts and at the extreme forward end of the table.

GEORGE RAW. 

